In the sewage treatment industry, clarifier tanks are used to remove solid waste from the water. Typical clarifier tanks as shown in FIG. 1, employ a main tank, an agitation device, optional density baffles, and an effluent trough. In use, raw or semi-treated water is pumped into the bottom center of the tank. Density baffles and gravity assist in holding down solids. The cleaner water then spills over into the effluent trough (usually, but not necessarily, located along the upper outer circumference of the tank) and off to further treatment. In order to reduce buildup of algae and other such unwanted contaminants caused by light, a cover is usually disposed over the effluent trough to block sunlight.
However, as shown in FIG. 2, a newer type of clarifier tank, includes a double trough system, whereby a first outer wall trough around the upper circumference is used as an influent trough (instead of a bottom fed tank) and a second attached effluent trough is located inboard of the influent trough for receiving the clarified outgoing water. These two troughs are divided by an upwardly extended dividing wall. In one arrangement, the upwardly extending dividing wall is non-circular, such that the relative widths of the influent and effluent troughs vary with respect to one another.